1. What are GPE and KE and how do I use the equations?
Starter:
Round the room:
TIME TO BEAT :

2. Learning outcomes explain that energy is conserved
describe energy transfers from kinetic to potential and vice versa and calculate the kinetic and potential energy involved
use the equation for kinetic energy

3. What is gravitational potential energy ?
describe energy transfers from kinetic to potential and vice versa and calculate the kinetic and potential energy involved

4. Engage brain
If work done = energy transferred what is the equation for working out the gain in GPE? Tip: check your notes on work done.

5. GPE Change in GPE (J) = weight (N) x height (m) This is the same as
Work done (J) = weight (N) x distance (m)
Don’t forget :
Weight = mass x gravitational strength (10)

6. Examples – on earth g = 10 N/Kg
If Mia lifts a 100 N box onto a table 2 m high. How much G.P.E. has the box gained?
Get pupils to answer them on the board

7. It’s race time !

8. Dougie weighs 800N and is standing at the top of a tall building
Dougie weighs 800N and is standing at the top of a tall building. He has 96000J of G.P.E. How tall is the building?
120m

9. Danny is on a diet. He runs to the top of 4 flights of stairs 5 times a day. At the top of the stairs at 70m, he has 59500J of GPE. What is his new weight? Danny is on a diet. He runs to the top of 4 flights of stairs daily. At the top of the stairs at 70m, he has 59500J of GPE. What is his new weight?
850N 85kg

10. Tom throws his guitar in the air at the end of the concert
Tom throws his guitar in the air at the end of the concert. It reaches 5m in height. It gains 2500J of GPE at the highest point. What is the mass of the guitar?
50kg (500N)

11. Harry likes to jump. His best jump is 150 cm. His mass is 75kg
Harry likes to jump. His best jump is 150 cm. His mass is 75kg. How much GPE does he gain at the highest point of his jump?
1125J

12. Kinetic Energy KE (J) = 0.5 x mass x (velocity) 2
use the equation for kinetic energy

13. The Law of Conservation of Energy
You cannot make or destroy energy. You can only change its type.
explain that energy is conserved

14. Gravitational potential energy
When you lift an object up . . .
. . . you increase its gravitational potential energy.
change in gravitational potential energy = weight  vertical height difference
explain that energy is conserved

15. use the equation for kinetic energy
Falling
If you let the object fall . . .
. . . it loses gravitational potential energy . . .
. . . and gains kinetic energy.
kinetic energy = ½  mass  speed2
use the equation for kinetic energy
explain that energy is conserved

16. explain that energy is conserved
Lifting a bag of flour
Lift up a 1 kg bag of flour to a height of 2 m.
change in gravitational potential energy
= weight  vertical height difference =
explain that energy is conserved

17. explain that energy is conserved
Now drop the bag of flour
As it falls, it loses gravitational potential energy . . .
. . . and gains kinetic energy
gain in kinetic energy
= loss of gravitational potential energy =
explain that energy is conserved

18. use the equation for kinetic energy
What speed does it reach?
kinetic energy = 20 J
½  mass  speed2 = 20 J
use the equation for kinetic energy
explain that energy is conserved

19. use the equation for kinetic energy
What speed does it reach?
kinetic energy = 20 J
½  mass  speed2 = 20 J
mass  speed2 = 40
speed2 = 40 (m/s)
speed = √40 m/s
speed = 6.32 m/s
use the equation for kinetic energy
explain that energy is conserved

20. Jamaica has a Bobsleigh team
Aim: to find out how much speed the Jamaican bobsleigh team reached in their qualifying race. You need to : Work out the GPE, KE and use this to find out the Speed of the bobsleigh. Info: Height: m Mass: 390 Kg Gravitational Pull : you know that!
Video from 1.41
explain that energy is conserved

21. Find Someone Who